James P. Sullivan, or Sulley for short, Although his is to scare children, Sulley makes efforts to befriend Boo, and then goes to extreme measures to protect her from Randall. It is Sulley, who realizes that making children laugh is a far better way to produce energy than making them scream, thus solving Monstropolis' energy crisis.
Sulley is also very loyal to Mike, going so far as to lend him "odorant" and making reservations for him at an exclusive restaurant on Mike's girlfriend's, Celia Mae, birthday. Sulley also attempts to cover for Mike when Mike realizes that he has forgotten to turn in his paperwork. In return, he relies on Mike to help him in his madcap efforts to keep Boo safe from Randall. When Mike protests, Sulley chooses to help Boo over appeasing Mike's pride; his choice is justified when Mike later changes his mind and comes to help him and Boo.
- Michael "Mike" Wazowski is Sulley's best friend and working partner at Monsters, Inc. He is Celia Mae's boyfriend and is constantly watched by Roz who seems to dislike him for always bringing in paperwork late. While at Harryhausen's for Celia's birthday, Sulely appeared out of nowhere to tell Mike that he had lead a human girl into the Monster World. Putting her into a Monsters, Inc. gym bag, Sulley tried to show him, but the human girl got out of the bag and wreaked havoc all over the resturant. The two secretly took her out of the resturant before the C.D.A. found her and disinfected the entire resturant.
When they learn that their boss Mr. Waternoose and Randall are in on a scam of draining children of screams, while Sulley tricks Waternoose into confessing, Mike records the confession and smugly replays it to watching C.D.A agents.
Mike proves to be not only a great assistant but a great ‘laugher’